This invention relates to fuser members for fusing toner images in imaging apparatus. This invention also relates to methods of making the fuser members. 2. Description of Related Art
In electrostatographic imaging apparatus, a light or digital image of an original to be copied is recorded as an electrostatic latent image on a photosensitive member and the latent image is subsequently rendered visible by the application of toner to the photosensitive member. The toner image is then fixed or fused upon a support. The support can be, for example, the photosensitive member itself or a support sheet, such as paper.
Thermal energy is generally used to fix toner images onto support members. To permanently fuse toner material onto a support surface by the application of heat, the toner material is heated to cause the toner to flow into the support member. During cooling of the toner material, it solidifies and becomes firmly bonded to the support.
Fillers have been added to outer (fusing) layers in fuser members for electrostatographic imaging apparatus to increase the thermal conductivity of these layers. See, for example, U.S. Pat. Nos. 6,002,910 and 6,007,657, which are each incorporated herein by reference in their entirety. By increasing thermal conductivity of the outer layers, the temperature needed to promote fusion of toner to supports is reduced. In addition, energy consumption is reduced. Increasing the thermal conductivity of outer layers also increases the speed of the fusing process by reducing the amount of time needed to heat the fuser member to a sufficient temperature to promote fusing.
Although fillers have been added to outer layers in fuser members to increase thermal conductivity, adding increasing amounts of filler also increases the hardness of the outer layer. Accordingly, for uses of fuser members in which excessive hardness of the outer layer is undesirable, the amount of filler added to the outer layer needs to be controlled to achieve the desired thermal conductivity of the outer layer, but without overly increasing hardness of the outer layer.
This invention provides fuser members having increased thermal conductivity.
This invention also provides fuser members having increased thermal conductivity and also desirable hardness.
This invention further provides fuser members having an outer layer that increases fusing speed. The fuser members also allow the use of reduced fusing temperatures at normal fusing speeds.
This invention also provides methods of making improved fuser members.
Exemplary embodiments of fuser members according to this invention comprise a substrate and an outer layer over the substrate. The outer layer comprises an elastomer and a filler material. The filler material comprises at least one ferromagnetic material and/or paramagnetic material. The filler material is anisotropically oriented in the outer layer. The outer layer has increased thermal conductivity in at least one direction as compared to outer layers comprising a filler material that is non-oriented, or randomly oriented.
Exemplary embodiments of methods of forming fuser members according to this invention comprise applying a liquid coating material over a substrate. The coating material comprises an elastomer and a filler material. The filler material comprises at least one ferromagnetic material and/or paramagnetic material. The coating material may optionally comprise a solvent. A magnetic field is applied to the coating material to orient the filler material in a selected orientation in the coating material. The coating material is cured with the filler material in the selected orientation to form an outer layer over the substrate, such that the filler material is oriented substantially in the selected orientation in the outer layer. The outer layer has increased thermal conductivity in at least one direction.